Rigging Tension Question

[richardbrennan]

I have been reading the Selden Guide on rig tuning and have a question. When the guide specifies set the tension to 20% of breaking strain, I assume that this refers to normal 1x19 stainless wire rigging. However, if you have Dyform or similar rigging the breaking strain is higher (quoted on a website I have looked at as 9770 compared to 7250 for 10 mm wire). My question is should on tension the rigging be set to the normal figure, in this case 1450 compared to 1954, on the assumption that the mast does not know what sort of wire you are using and that the higher figure might over tension the rig?

 

[KellysEye]

We had stainless rigging and I tigtened it using a large adjustable spanner until I couldn't tighten it anymore, it worked fine. I have no idea about Dyform in fact I've never heard of it.

 

[VicS]

I have been reading the Selden Guide on rig tuning and have a question. When the guide specifies set the tension to 20% of breaking strain, I assume that this refers to normal 1x19 stainless wire rigging. However, if you have Dyform or similar rigging the breaking strain is higher (quoted on a website I have looked at as 9770 compared to 7250 for 10 mm wire). My question is should on tension the rigging be set to the normal figure, in this case 1450 compared to 1954, on the assumption that the mast does not know what sort of wire you are using and that the higher figure might over tension the rig?

I would say that you should tighten it to the figure that applied to the original rigging. The same would apply if increasing the rigging wire gauge,

To tighten to 20% of the breaking strain of heavier or stronger rigging would possibly over stress the hull etc ........ and in many boats jam the bog door!

 

[BabaYaga]

I have been reading the Selden Guide on rig tuning and have a question. When the guide specifies set the tension to 20% of breaking strain, I assume that this refers to normal 1x19 stainless wire rigging. However, if you have Dyform or similar rigging the breaking strain is higher (quoted on a website I have looked at as 9770 compared to 7250 for 10 mm wire). My question is should on tension the rigging be set to the normal figure, in this case 1450 compared to 1954, on the assumption that the mast does not know what sort of wire you are using and that the higher figure might over tension the rig?

The guide actually mentions Dyform (Swedish version at least).
I read it as: Yes, go for 15 - 20% of breaking strain for the cap shrouds, however Dyform has lower stretch compared to normal 1x19.
If using the 2 meter tape measure method, 5% stretch is equal to 1mm for 1x19, 0,95mm for Dyform (and 0,7mm for rod).
So for tensioning to 20% of breaking strain you should measure 3,8mm for Dyform (compared to 4mm for 1x19).

 

[Allan]

A few years ago I delivered a boat with Dyneema Dux standing rigging. As this was new we had to re-tighten it a few times. Apparently this is due to the splices settling. We tightened it using the main, extremely large, multi speed winches on the mast. Setting the tension was simple, as the largest person there I would bounce up and down on the longest handle we had! Not very scientific but quite effective. The boat was an old ocean 50, ex Steve White.
Allan

 

[Tranona]

We had stainless rigging and I tigtened it using a large adjustable spanner until I couldn't tighten it anymore, it worked fine. I have no idea about Dyform in fact I've never heard of it.

So, why are you bothering to post this rubbish which does not answer the OPs question?

BTW amazed somebody who claims to know so much has never heard of Dyform - a long established type of stainless steel wire widely used on performance boats because of its greater strength and smooth finish..

BTW

 

[richardbrennan]

Many thanks to all for your replies.

The Selden Guide gives very clear values for the rig tension, at least for the cap shrouds and backstay, the tension in the lower caps seem to be determined by what is necessary to stop the leeward one going slack when close hauled, there is not much guidance on the upper intermediates. I am hoping to use a Loos Gauge, so I do not need suggestions as to how to judge the tension, just an answer as to which tension I should be aiming for. My thinking is along the lines of VicS at the moment.

 

[Ceirwan]

We had stainless rigging and I tigtened it using a large adjustable spanner until I couldn't tighten it anymore, it worked fine. I have no idea about Dyform in fact I've never heard of it.

That's an incredibly dumb thing to suggest.

For the Op if you do have a rig tension gauge I would set up with the tension that the original rigging would have had used and see how you get on. (as posted above by someone else)
If not then you can use the method of tightening the leeward shroud when hard on the wind.

If the boat was designed with Dyform then I'd suggest using the 20% figure for Dyform.

 

[richardbrennan]

Hi All

I have spoken to the guy at Salty John who are one of the suppliers of Loos Gauges in the UK. He was most helpful, the boat was not originally rigged with Dyform and he said to set it up with the original tensions. He said the same would apply if I had gone up a size in wire diameter.

Many Thanks to All

Rick

 

[[70521]]

BTW amazed somebody who claims to know so much has never heard of Dyform - a long established type of stainless steel wire widely used on performance boats because of its greater strength and smooth finish.

Thanks I often wondered what Dyform was; not being a user of performance boats I did not have a clue.

 

[Javelin]

Given your are looking at 15 to 20% I assume you have a fractional, swept spreader rig.
(non swept spreader rigs usually run on 10%.)

If so the caps and inters I'd tension to 15 to 18% with 1/19 wire and 18 to 20% for dyform of the same dia.
Remember this is just a static loading and also keep in mind the boat age / construction as well.
Some lightweight French and German boats with deck stepped masts won't take 15% let alone 20% if you still want to open the doors down below!
Only apply the static load to your caps, inters and lowers.
Do not tension anywhere near this on the back or baby stay.

If you have linked inters then its a little harder to get right and is a of bit trial and error getting the link to match the right vertical spreader angle.

 

[Tranona]

Thanks I often wondered what Dyform was; not being a user of performance boats I did not have a clue.

Not only performance boats - although that is the main market as it is stronger weight for weight but not as pricy and fickle as rod rigging. I had a Dyform forestay on my old wooden boat in the days of hanked on sails because of its smooth finish. Still have it coiled up in the garage having switched to furling 25 yeas ago!

 

[KellysEye]

>So, why are you bothering to post this rubbish which does not answer the OPs question?
>>That's an incredibly dumb thing to suggest.

When we renewed the rigging in Burham on Crouch the rigger used a spanner to tighten everything, he said a spanner doesn't apply enough power to do any damage and you can check it's tight enough if it doesn't move more than a quarter of an inch when you pull it. If you don't want to believe that, which you usually don't, that's fine pay out for a tension gauge.

 

[Ceirwan]

>So, why are you bothering to post this rubbish which does not answer the OPs question?
>>That's an incredibly dumb thing to suggest.

When we renewed the rigging in Burham on Crouch the rigger used a spanner to tighten everything, he said a spanner doesn't apply enough power to do any damage and you can check it's tight enough if it doesn't move more than a quarter of an inch when you pull it. If you don't want to believe that, which you usually don't, that's fine pay out for a tension gauge.

A rigger works with the materials he's using every day, chances are he knows his tools / strength.
No one says you need a tension gauge to do the rigging, there are plenty of of ways to do it without.

But simply stating 'oh just tighten it as much as you can' isn't going to produce a well tuned rig. Last time I checked spanners come in different sizes and not everyone is the same strength.
I know plenty of people that could wind a rig way past the recommended 20% even using a small spanner. Sure they probably won't break it, but the objective is a well tuned rig not just winding it on FT.

 

[Javelin]

You risk a myriad of problems not to mention a few very dangerous ones if the rig has not been set up correctly.
Sight up the track, is it dead straight laterally?
Is it inverted?
Does the pre-bend match your sail design? (usually 50 to 75mm at 50% of hoist)
We see it quite often where a badly set up rig has damaged the boat, with bent and twisted chain plates, cracked glass and gel due to excessive movement, leaks etc.

Many furler issues are due to incorrect tensions or a badly replaced forestay.
Pro furl are very easy to get wrong as are old Hood furlers.

The Oyster 435 I delivered on Sunday which had been rigged in Ipswich late last year was frankly dangerous with wildly differing tensions and split pins missing.
I de-rigged a Sadler 26 last August and because the tensions felt so high on the bottle screws I checked with the gauge and the caps had been set at 44% of breaking strain on a masthead non-swept back rig. (it should have been 10%)

So I would personally run a mile if the riggers tool set only comprised of a spanner and a screw driver.

 

[Birdseye]

I have been reading the Selden Guide on rig tuning and have a question. When the guide specifies set the tension to 20% of breaking strain, I assume that this refers to normal 1x19 stainless wire rigging. However, if you have Dyform or similar rigging the breaking strain is higher (quoted on a website I have looked at as 9770 compared to 7250 for 10 mm wire). My question is should on tension the rigging be set to the normal figure, in this case 1450 compared to 1954, on the assumption that the mast does not know what sort of wire you are using and that the higher figure might over tension the rig?

Whilst the Dyform might be a bit stronger your boat hull and mast is not changed. So tensioning to an approximately 30% greater load will bend the boat a bit more before the extra loads from sailing come on in addition. Seems unlikely to me that this would overstrain
the hull at rest since the loads in a blow will take the original rig up to higher than that. Could be a different issue in extremis if you did increase rig tension with the Dyform . Personally I would load the Dyform to the loads of the original wire. Thats what the rig designer will have based his calx on.